Human power

Human power is work or energy that is produced from the human body. It can also refer to the power (rate of work per time) of a human. Power comes primarily from muscles, but body heat is also used to do work like warming shelters, food, or other humans. Human power is work or energy that is produced from the human body. It can also refer to the power (rate of work per time) of a human. Power comes primarily from muscles, but body heat is also used to do work like warming shelters, food, or other humans. World records of power performance by humans are of interest to work planners and work-process engineers. The average level of human power that can be maintained over a certain duration of time⁠  — say over the extent of one minute, or one hour⁠ ⁠— is interesting to engineers designing work operations in industry. Human power is occasionally used to generate, and sometimes to store, electrical energy in batteries for use in the wilderness. Normal human metabolism produces heat at a basal metabolic rate of around 80 watts. During a bicycle race, an elite cyclist can produce close to 400 watts of mechanical power over an hour and in short bursts over double that — 1000 to 1100 watts; modern racing bicycles have greater than 95% mechanical efficiency. An adult of good fitness is more likely to average between 50 and 150 watts for an hour of vigorous exercise. Over an 8-hour work shift, an average, healthy, well-fed and motivated manual laborer may sustain an output of around 75 watts of work. However, the potential yield of human electric power is decreased by the inefficiency of any generator device, since all real generators incur considerable losses during the energy conversion process. While attempts have been made to fit electric generators to exercise equipment, the energy collected is of low value compared to the cost of the conversion equipment. Several forms of transport utilize human power. They include the bicycle, wheelchair, walking, skateboard, wheelbarrow, rowing, skis, and rickshaw. Some forms may utilize more than one person. The historical galley was propelled by freemen or citizens in ancient times, and by slaves captured by pirates in more recent times. The MacCready Gossamer Condor was the first human-powered aircraft capable of controlled and sustained flight, making its first flight in 1977. In 2007, Jason Lewis of Expedition 360 became the first person to circumnavigate the globe at non-polar latitudes using only human power — walking, biking, and rollerblading across the landmasses; and swimming, kayaking, rowing, and using a 26-foot-long pedal-powered boat to cross the oceans. Some equipment uses human power. It may directly use mechanical power from muscles, or a generator may convert energy generated by the body into electrical power. Human-powered equipment consists of electrical appliances which can be powered by electricity generated by human muscle power as an alternative to conventional sources of electricity such as disposable primary batteries and the electrical grid. Such devices contain electric generators or an induction system to recharge their batteries. Separate crank-operated generators are now available to recharge battery-powered portable electronic devices such as mobile phones. Others, such as mechanically powered flashlights, have the generator integrated within the device. An alternative to rechargeable batteries for electricity storage is supercapacitors, now being used in some devices such as the mechanically powered flashlight shown here. Devices that store the energy mechanically, rather than electrically, include clockwork radios with a mainspring, which is wound up by a crank and turns a generator to power the radio.